1. Field of the Invention
This invention relates generally to air gauging equipment and more particularly is directed towards a new and improved attachment for the nozzle of air gauging apparatus to adapt the apparatus for use with thin, fragile films and rough or irregular surfaces.
2. Description of the Prior Art
Extremely precise gauging of travelling webs, sheet strips, and the like, can be made without physically contacting the work by use of an air follower of the sort disclosed in my U.S. Pat. No. 3,194,055. The follower is a pneumatic servo-mechanism which provides non-contact gauging with only a stream of air touching the part to be measured. The air gap between the nozzle tip and the work controls the position of the piston in a double-acting air cylinder. A shaft connected to the piston drives the displacement measuring device, typically a dial indicator.
The air stream delivered from the nozzle typically is supplied at 35 psi, which, while useful in blowing away dirt, oil or other residue, in many instances applies too much force on delicate or resilient parts to prevent an accurate measurement. In such cases, the air pressure is lowered to the order of 1 psi and this lower pressure is subsequently converted to a high pressure in order to actuate the follower.
However, even at this low pressure the apparatus cannot be used to gauge extremely thin sheets such as plastic film less than 0.001 inch thick. The breeze from the nozzle may blow away the sample and the Bernouille effect tends to lift the sample from its supporting platform.
Also, the gap in air gauging devices of this type is influenced to some degree by the smoothness or roughness of the surface of the work being gauged. Thus, there may be some ambiguity using a smooth gauge block as a standard for gauging work with a rough surface. The work surface which is rough or irregular thus has a varying thickness between a diminutive series of hills and valleys.
It is an object of the present invention to provide an attachment for use with air gauge followers which allows the follower to be used in gauging work of a thin, fragile nature. Another object of this invention is to provide an attachment for use with an air gauging system for gauging work characterized by a rough or irregular surface.